The present invention generally relates to improved constructions for a deflectable, high torque catheter. More particularly, this invention relates to methods and catheters for diagnosing and treating cardiac arrhythmias via a multi-directional, deflectable, torque transmittable cardiovascular catheter by mapping and stimulating the human heart with pacing, cardioversion, defibrillation, and/or radiofrequency ablation therapy.
Symptoms of abnormal heart rhythms are generally referred to as cardiac arrhythmias, with an abnormally rapid heart beat being referred to as tachycardia. The present invention is concerned with the treatment of tachycardias that are frequently caused by the presence of an xe2x80x9carrhythmogenic sitexe2x80x9d or xe2x80x9caccessory atrioventricular pathwayxe2x80x9d close to the surface of the upper chambers of a heart. The heart includes a number of normal pathways that are responsible for the propagation of electrical signals from the upper chamber to the lower chamber necessary for performing normal systole and diastole functions. The presence of arrhythmogenic site or accessory pathway can bypass or short circuit the normal pathway, potentially resulting in very rapid heart contractions, referred to here as tachycardias.
Treatment of tachycardias may be accomplished by a variety of approaches, including drugs, surgery, implantable pacemakers/defibrillators, and catheter ablation. Catheter based radiofrequency ablation is generally performed after conducting an initial electrophysiology study where the locations of the arrhythmogenic site and/or accessory pathway are determined. Electrophysiology study and temporary defibrillator/cardioverter involve catheters having at least one electrode means for the delivery of low energy pacing pulses directly to the heart tissue at various intervals or frequencies in order to induce the arrhythmia. Once the arrhythmia is induced, it must be terminated by typically delivering a high-energy defibrillation shock across the patient""s chest with paddles. A specific very high therapeutic voltage is required within the heart to terminate the induced arrhythmias. The voltage delivered through a conventional transthoracic defibrillator paddle from outside the body is substantially greater than the necessary therapeutic voltage because it needs to compensate for the energy losses through the skin and the thoracic cavity. An internal defibrillator/cardioverter from a catheter poses less risk and higher therapeutic efficiency.
A transvenous catheter that combines the functions of the rate sensing, pacing, and defibrillation has a plurality of electrodes on a distal portion. The catheter should have multi-directional deflectability and high torque so that it can be guided to the exact location of the heart tissue for pacing, cardioversion, defibrillation and/or radiofrequency ablation. The catheter should also be flexible enough for insertion into a body and have adequate surface for contacting the intracardiac tissues. Some examples of cardioverter and methods are U.S. Pat. No. 5,005,587 to Scott, U.S. Pat. No. 5,766,224 to Alferness et al., U.S. Pat. No. 5,814,081 to Ayers et al., U.S. Pat. No. 5,810,887 to Accorti, Jr. et al., and U.S. Pat. No. 5,913,887 to Michel. Because of the exact location requirements, the deflectability and torque transmission properties of a catheter to ensure that a substantial fraction of the rotational and displacement forces provided along the catheter are translated to rotational and displacement forces at the distal end of said catheter become very important.
Another particular interest point to the present invention is radiofrequency (RF) ablation protocols that have proven to be highly effective in tachycardia treatment while exposing a patient to minimal side effects and risks. After a mapping study, an ablation catheter is usually introduced to the target heart chamber and is manipulated so that the ablation tip electrode lies exactly at the target tissue site. Radiofrequency energy or other suitable energy is then applied through the electrode to the cardiac tissue in order to ablate the tissue of arrhythmogenic site or the accessory pathway. By successfully destroying that tissue, the abnormal conducted signal patterns responsible for the tachycardia can be eliminated. In the case of atrial fibrillation (AFib), multiple arrhythmogenic sites and/or multiple accessory pathways exist. It becomes desirable that a long linear lesion or a broad lesion zone at the tissue contact sites to ensure appropriate energy delivery.
Scott in U.S. Pat. No. 5,005,587 discloses a braided electrode lead in an endocardial pacing and defibrillation catheter having an elongated hollow polyurethane shaft. Although providing good stiffness and biocompatibility, the polyurethane tube lacks sufficient translation between the rotational and displacement forces applied along the body of the polyurethane tube. Accorti Jr. et al. in U.S. Pat. No. 5,810,887 discloses a catheter having a braided wire section for torque transmission. For the purposes of cardioversion and defibrillation, the surface contact area becomes very critical. With regards to the braided wire section, only the outer radial surface of the braided section is employed in contacting a tissue. In other words, the effective tissue-contacting surface of wires in the braided wire section is sub-optimal as compared to an essentially flat surface. The braiding of wires also makes the braided wire section undesirably rigid.
Similarly, Michel in U.S. Pat. No. 5,913,887 discloses a transvenous device having three coil electrodes for cardioversion of atrial flutter or atrial fibrillation. The tissue-contacting surface area of a coil electrode is less than an essentially flat surface. The coil electrode also suffers a drawback of less torque transmission property. None of the conventional temporary catheters for cardioversion/defibrillation has a steerability property.
While cardioversion and defibrillation procedures using an existing catheter design have produced some promising results, the bending and torque transmission properties, the effective tissue-contacting surfaces, and rigidity of a conventional catheter usually do not meet the clinical requirements. Therefore, there is an urgent clinical need to have a flexible catheter that also possess multi-directional deflectablility and high torque transmitting property to be used in cardioversion and defibrillation procedures.
The present invention provides an improved deflectable and high torque catheter that can be used in the procedures of stimulating the human heart with pacing, cardioversion, defibrillation and/or radiofrequency ablation therapy. It is one object of the present invention to provide a flexible catheter with high torque transmission properties. It is another object of the present invention to provide a flexible catheter with a slit tubular element that has a plurality of rows of slits and anchors on said slit tubular element. It is still another object of the present invention to provide a flexible catheter with a slit tubular element that has at least one continuously spiraling slit with longitudinal rows of anchors on said slit tubular element. The word xe2x80x9cslitxe2x80x9d is defined as a straight or curved narrow cut or opening on a substrate in this patent application.
In one embodiment, a deflectable, high torque catheter comprises a flexible catheter shaft having a distal shaft section, a proximal shaft section and at least one middle shaft section, wherein each shaft section has a distal end and a proximal end, and wherein the shaft section is secured to its adjacent shaft section, said flexible catheter shaft having at least one lumen extending between the distal end of the distal shaft section and the proximal end of the proximal shaft section. A handle may be secured at the proximal end of the proximal shaft section. The catheter further comprises at least one shaft section comprising a deflectable, high torque transmission assembly for transmitting deflectability and torque along said at least one shaft section, said deflectable and high torque transmission assembly comprising a slit tubular element that has a plurality of staggered rows of slits and anchors on said slit tubular element and has sufficient deflectability and torque properties ensuring that a substantial fraction of the rotational, displacement, and bending forces provided along said at least one shaft section are translated to rotational, displacement, and bending forces at the distal end of said shaft section of the flexible catheter shaft. The deflectable, high torque catheter of the present invention is equally useful as either a non-energy delivery catheter or an energy delivery catheter.
In another embodiment, said deflectable and high torque transmission assembly comprises a slit tubular element that has at least one continuously spiraling slit on said slit tubular element and has sufficient bending and torque properties ensuring that a substantial fraction of the rotational, displacement, and bending forces provided along said at least one shaft section are translated to rotational, displacement, and bending forces at the distal end of said shaft section of the flexible catheter shaft, wherein the slit tubular element has a plurality of parallel, staggered rows of slit members and anchors resulting from the at least one continuously spiraling slit.
In a preferred embodiment, the arrangement of said plurality of staggered rows of slits with respect to a longitudinal axis of said shaft section of the catheter may be selected from the group consisting of a perpendicular slit, an angled slit, a curved slit, and a combination of the above thereof Furthermore, each of the plurality of slits has a slit starting point at an outer surface of said shaft section and two slit terminating points at said outer surface away from the slit starting point, wherein the distances from said slit starting point to each of the two slit terminating points are about equal. In a further embodiment, the at least one slit terminating point is coupled with a small circular hole for even stress release, especially when the slit tubular element is bent in one direction or the opposite direction.
In a particularly preferred embodiment, the slit tubular element of the deflectable, high torque transmission assembly is embedded within an elastic membrane, is covered on an inner side of the slit tubular element, or is covered on an outer side of the slit tubular element by an elastic membrane. In one embodiment, the elastic membrane is to separate the interior lumen of the slit tubular element from an exterior surrounding of said slit tubular element. The elastic membrane may be selected from the group of elastic material or expandable membrane consisting of silicone, latex, polyurethane, thermoplastic elastomer such as Pebax brand polyether block amides, polyethylene balloon, cross-linked polyethylene balloon, permeable membrane, polyethylene terephthalate balloon, and the like. The slit tubular element may be made of a material selected from the group consisting of polypropylene, polysulfone, platinum, stainless steel, Nitinol, gold, silver, iridium, tungsten, and their mixture thereof.
The deflectable, high torque catheter of the present invention further comprises a RF energy generator and an electrical conductor secured to said RF energy generator and said slit tubular element, wherein the electrical conductor is adapted for transmitting RF energy from said RF energy generator to the slit tubular element which is constructed of a conductive material. The high torque catheter further comprises at least one electrode mounted on the catheter shaft that is adjacent to the slit tubular element. The at least one electrode and/or the slit tubular element may be used for sensing, pacing, cardioversion, defibrillation and RF energy delivery.
In still another embodiment, the catheter further comprises a steering mechanism on the handle for deflecting the distal section of the catheter. One end of the steering wire is usually secured at said steering mechanism, while the other end is secured at a distal point on the inner side of the distal shaft section; in between the two ends, the steering wire travels through a row of anchors inside the said slit tubular element for deflecting the distal portion of said flexible high torque catheter in one specific plane. The catheter may further comprise other steering wires traveling through other rows of anchors attached to the slit tubular element to allow deflectability in other planes. The catheter may further comprise a plurality of deflectable curves on the distal tip section of the catheter shaft being provided by the steering mechanism on the handle. By providing a steerable catheter with a plurality of multi-directional, deflectable curves, the catheter can fit the ventricle contours appropriately. The steering mechanism is well known to those who are skilled in the art. However, incorporation of a multi-planar, steering mechanism into a high torque catheter of the present invention is unobvious.
A method for operating a deflectable, high torque catheter within a body of a patient may comprise the steps of: (a) percutaneously introducing the deflectable, high torque catheter through an opening of the body of the patient; (b) approaching the deflectable, high torque catheter to a target tissue of the patient by transmitting rotational and displacement forces through the at least one shaft section of the flexible catheter shaft; and (c) positioning the deflectable, high torque catheter at the target tissue for diagnostic and/or therapeutic tissue treatment. Said deflectable, high torque catheter comprises a flexible catheter shaft having a plurality of shaft sections, wherein at least one shaft section comprises a high torque transmission assembly for transmitting torque along said at least one shaft section, said high torque transmission assembly comprising a slit tubular element that has a plurality of rows of slits and anchors on said slit tubular element and has sufficient torque properties and multi-directional deflectability ensuring that a substantial fraction of the rotational, displacement, and bending forces provided along said at least one shaft section are translated to rotational, displacement, and bending forces at a distal end of said shaft section.
The method and apparatus of the present invention have several significant advantages over known conventional catheters or techniques, particularly the flexible and multi-directional deflecting slit tubular element on at least one shaft section of the flexible catheter make the catheter particularly useful in procedures for stimulating the human heart with pacing, cardioversion, defibrillation, and/or radiofrequency ablation.